To change your computer desktop's wallpaper, decide which of the images you want to use then click on the resolution (800x600, 1024x768 etc.) that's right for your computer.

Your browser will then display a larger version of the image. Right-click on the image and choose to 'Set as Wallpaper'.

Hint: if you aren't sure of your computer screen's resolution, choose 800x600 and if it looks too small once it's on your desktop, go up to 1024x768.